| Dear
EarthTalk: Alternative energy sources like wind
power, hydrogen and biofuels are getting a lot of headlines
these days, but what about efforts to generate electricity
from the ocean’s waves?
-- Tina Cook, Naples, FL
As
any board or body surfer will tell you, the ocean’s
tidal currents pack considerable wallop. So why wouldn’t
it make sense to harness all that formidable power, which
is not too unlike that of the rivers that drive hydropower
dams or the wind that drives wind turbines, to make energy?
The
concept is simple, says John Lienhard, a University of Houston
mechanical engineering professor: “Every day the moon’s
gravitational pull lifts countless tons of water up into,
say, the East River or the Bay of Fundy. When that water flows
back out to sea, its energy dissipates and, if we don’t
use it, it’s simply spent.” According to Energy
Quest, an educational website of the California Energy Commission,
the sea can be harnessed for energy in three basic ways: using
wave power, using tidal power, and using ocean water temperature
variations in a process called “ocean thermal energy
conversion” (OTEC).
In
harnessing wave power, the back-and-forth or up-and-down movement
of waves can be harnessed, for example, to force air in and
out of a chamber to drive a piston or spin a turbine that
can power a generator. Some systems in operation now power
small lighthouses and warning buoys. Harnessing tidal energy,
on the other hand, involves trapping water at high tide and
then harnesses its energy as it rushes out and drops in its
change to low tide. This is similar to the way water makes
hydroelectric dams work. Already some large installations
in Canada and France generate enough electricity to power
thousands of homes.
An
OTEC system uses temperature differences between deep and
surface waters to extract energy from the flow of heat between
the two. An experimental station in Hawaii hopes to develop
the technology and someday produce large amounts of electricity
on par with the cost of conventional power technologies.
Proponents
say that ocean energy is preferable to wind because tides
are constant and predictable and that water’s natural
density requires fewer turbines than are needed to produce
the same amount of wind power. Given the difficulty and cost
of building tidal arrays at sea and getting the energy back
to land, however, ocean technologies are still young and mostly
experimental. But as the industry matures, costs will drop
and some analysts think the ocean could power nearly two percent
of U.S. energy needs.
Several
companies now work at the cutting edge of ocean power technology.
Scotland’s Ocean Power Delivery Ltd. has a wave system
called Pelamis that it hopes to install in waters off of California’s
wave-battered central coast. And Seattle, Washington’s
Aqua Energy has installations off the coasts of Oregon, Washington
and British Columbia and is in talks with utilities about
providing the Pacific Northwest with hundreds of megawatts
of ocean energy within the next decade.
Tidal
energy pioneers are also hard at work on the U.S. Atlantic
coast. The New Hampshire Tidal Energy Company is developing
tidal power in the Piscataqua River between New Hampshire
and Maine. And a company called Verdant Power is providing
Long Island City, New York with electricity through tidal
river turbines and has begun installation of tidal power systems
in New York City’s East River.
CONTACTS:
Ocean Power Delivery Ltd., www.oceanpd.com;
Aqua Energy (Finavera Renewables), www.finavera.com/wave;
Verdant Power, www.verdantpower.com.
PHOTO
COURTESY OF GETTY IMAGES
The
cumulative effect of millions of inefficient motorboats plying
our waterways has been devastating to marine life and our
water supplies.
Dear EarthTalk:
There has been so much attention paid to designing environmentally
friendly cars. Is there a similar effort to replace gas-guzzling
boats? -- Brita B., via e-mail
The U.S. has been
regulating fuel economy and emissions in cars and trucks for
decades but got a late start addressing similar issues with
boats. In 1996, though, recognizing a growing problem of boat
engine pollution, the Environmental Protection Agency (EPA)
issued new rules to “bring forth a new generation of
marine engines featuring cleaner technology and providing
better engine performance to boat owners.”
Even small quantities
of fuel and exhaust discharged by boats can disrupt the balance
of nutrients, oxygen and clean water in both freshwater and
marine ecosystems. Indeed, the cumulative effect of millions
of inefficient motorboats plying our waterways has been devastating
to marine life and our water supplies. Under the new EPA regulations,
which will phase in over the next 30 years, new marine engines
will burn gas much more efficiently and generate much less
pollution than most models out on the water today.
According to the
EPA, traditional two-stroke boat engines waste significant
amounts of gasoline and oil, spilling as much as 30 percent
of their fuel into the water and air either unburned or partially
unburned. In the water, unburned hydrocarbons increase concentrations
of benzene, methyl tertiary-butyl ether (MBTE) and other toxic
substances that pollute water ecosystems. In the air, they
help form smog, which causes a host of health problems and
disrupts visibility everywhere from our cities to our national
parks.
Those looking to
buy a boat today should choose one with a four-stroke or direct
fuel injection (DFI) two-stroke engine. These pollute about
75 percent less than their traditional two-stroke predecessors
and use as much as 50 percent less gas and oil. They cost
more than traditional two-stroke engines, but owners soon
make up the difference in fuel and oil savings. They are also
easier to start and maintain, and are quieter.
New generations
of electric boat motors are also coming on line, and promise
to significantly cut pollution if adopted widely. Wooden,
sport and leisure boats are now all available with electric
engines that are quite comparable to traditional engines in
performance and looks. They are also non-polluting, quiet
and can cruise where gas motors are not permitted. Some leading
makers include Beckman, Budsin, Cobalt Marine, Electric Launch,
Duffy, Electracraft, Griffin Leisure, Pender Harbour and Spincraft.
The only catch
is that the energy that powers the batteries for electric
boats most likely comes from a coal-burning power plant that
spews mercury, carbon dioxide and other pollutants into the
skies and waterways. A handful of manufacturers--such as Australia’s
Solar Sailor and Canada’s Tamarack Lake--now make solar-powered
or solar-assisted electric boats to help overcome this environmental
hurdle.
Of course, the
ultimate energy source for any recreational activity is elbow
grease. But for those who need more than a canoe or kayak
to get around, Nauticraft hybrid boats employ human pedal
power to augment a small electric motor. And the Italian-made
Shuttle Bike puts a new spin on pedal boats: Owners affix
two inflatable pontoons to their mountain bikes, and they
can then pedal around their local lake or harbor.
CONTACTS:
EPA: Shipshape Shores and Waters: A Handbook for Marina Operators
and Recreational Boaters, www.epa.gov/owow/nps/marinashdbk2003.pdf. |
